I run 2S Lipo RX packs and HV servos on my E7 and soon E750 stretch. On the E7 with my big air, sport, FFF style, I can get 6 flights comfortably, 8 if I am not paying attention. I don't like to push RX packs, too much riding on them. No reason to anyway, they are cheap, just have two. They recharge fast compared to the flight packs.